As two of the basic senses of human beings, olfaction and gustation play a very important role in daily life. These two types of chemical sensors are important for recognizing environmental conditions. Electronic nose and electronic tongue, which mimics animals’ olfaction and gustation to detect odors and chemical components, have been carried out due to their potential commercial applications for biomedicine, food industry and environmental protection. In this report, the biomimetic artificial nose and tongue is presented. Firstly, the smell and taste sensors mimicking the mammalian olfaction and gustation was described, and then, some mimetic design of electronic nose and tongue for odorants and tastants detection are developed. Finally, olfactory and gustatory biosensors are presented as the developing trends of this field.

Semiconducting qusi‐1D chemiresistors are nearly ideal substances for deployment of self‐heating effect in gas sensorics. The latter is due to beneficial morphology of the nanowires, which hampers thermal losses to the environment, substrate and metal leads. Since the self‐heated nanowire
sensor device does not require an external heater, this effect can be used to fabricate nanoscopic sensors operable at room temperature with ultra‐small power consumption. The analysis of the heat partitioning in self‐heated nanowire device indicate the existence of its optimal architecture where power consumption of few μW is achievable in air.

Nanotechnology is in continuous evolution leading to production of quasi‐one dimensional (Q1D) structures in a variety of morphologies: nanowires, nanotubes, nanobelts, nanorods, nanorings, hierarchical structures. In particular, metal oxides represent an appealing category of materials with properties from metals to semiconductors and covering practically all aspects of material science and physics in areas including superconductivity and magnetism. MOX nanowires are crystalline structures with well‐defined surface terminations, chemical composition and almost dislocation and defect free. Due to their nanosized dimensions, they can exhibit properties significantly different from their coarse‐grained polycrystalline counterpart. The increase in the specific surface causes an enhancement of the surface related properties, such as catalytic activity or surface adsorption, key properties for solid‐state gas sensors development. The use of MOX nanowires as gas‐sensing materials should reduce instabilities, suffered from their polycrystalline counterpart. The gas experiments confirm good sensing properties and the real integration in low power consumption transducers.

In surface ionization (SI) gas detection adsorbed analyte molecules are converted into ionic species at a heated solid surface and extracted into free space by an oppositely biased counter electrode. In the present work we consider the formation of positive and negative analyte gas ions at
surfaces. We find that SI leads to positive ion formation only, with the SI efficiency scaling with the ionization energy of the analyte gas molecules. Aromatic and aliphatic hydrocarbons with amine functional groups exhibit particularly high SI efficiencies.

In this paper we discuss the combined use of integrated CMOS microhotplates employing nanomaterial sensing layers for intelligent, compact gas sensors with increased sensitivity, selectivity and fast response times. We first review the status of nanomaterial‐based gas sensors, their operating principles, discussing growth issues and their compatibility with CMOS substrates. We then describe Multiwall (MW) Carbon Nanotubes
(CNTs) and ZnO
Nanowires (NW) growth/deposition onto CMOS microhotplates. The paper continues by discussing the response of these nanomaterial sensing layers to vapours and gasses. Finally we discuss the future prospects of nanomaterial‐based CMOS
gas sensors, highlighting on one hand their future potential and on the other hand their present shortcomings and future challenges that need to be addressed before they can be released commercially.

The effect of environmental humidity on sensor signal to 1000 ppm of
in air was investigated in a wide range of relative humidity (RH) and sensor operation temperature. To prepare sensing material we used highly dispersed nano‐
with 3–5 nm particle size and surface area
Blank
doped with Pd 1%, and
doped with Pt 1% were used as materials for sensors. FTIR
spectroscopy was employed to study water chemisorption on the surface of blank and doped
Sensor signal measurements were performed in conditions close to equilibrium at 0, 20, 50 and 80% RH in the temperature range 30–600° C. The effect of humidity on
detection mechanism is discussed.

Mixed‐potential behavior of the water quality monitoring sensors using nanostructured
sensing electrode (SE) has been observed in strong alkaline solutions at dissolved oxygen (DO) measurements in the temperature range of 9–30° C. This behavior indicated that a Faradaic oxygen reduction reaction becomes not only a one‐electron process, which is typical for DO measurements at a neutral pH, but rather multi‐step process with superoxide oxygen ions
and
ions involvement. The DO sensing characteristics were examined in the pH range of 2.0–13.0. The measured
emf
at strong alkaline solutions is a mixed potential from the reactions involved
and
ions and DO. Impedance spectroscopy was employed for confirmation the mixed‐potential behavior of the sensor. It was also found during experiments that
ions influence the response/recovery rate of the SE reactions as the pH of water increases.

Carbon nanotubes
(CNTs) have been proposed for a broad spectrum of applications, including chemical sensing. Here we report on an investigation of multi‐walled CNTs
(MWCNTs) as conductive filler for composite
polymer sensing films. Such materials combine conductive fillers with an insulating polymer to produce a chemically sensitive, electrically conducting material. These polymer
composites offer several important advantages for chemical sensing, including room temperature operation (hence ultra low power), a broad range of selectivities (due to the wide choice of available polymers), and low manufacturing cost. Our approach is to compare the sensing qualities of these composite
films, in resistive and field‐effect configurations, with existing carbon black polymer
composites. Their responses to propanol and toluene vapour in air show that the carbon black resistive sensors outperform CNT
sensors by a factor of four in response magnitude. Thus we conclude that for these vapours and using this sensor fabrication method, carbon black polymer
composite
films are preferable for chemical sensing than MWCNT
polymer
composites.

Sample pre‐treatment is a typical procedure in analytical chemistry aimed at improving the performance of analytical systems. In case of gas sensors sample pre‐treatment systems are devised to overcome sensors limitations in terms of selectivity and sensitivity. For this purpose, systems based on adsorption and desorption processes driven by temperature conditioning have been illustrated. The involvement of large temperature ranges may pose problems when QMB gas sensors are used. In this work a study of such influences on the overall sensing properties of QMB sensors are illustrated. The results allowed the design of a pret‐reatment unit coupled with a QMB gas sensors array optimized to operate in a suitable temperatures range. The performance of the system are illustrated by the partially separation of water vapor in a gas mixture, and by substantial improvement of the signal to noise ratio.

An easy‐to‐use and versatile analytical method for complex matrix analisis like coffee was developed. The system consists of a microtrap sample preparation, a home made simplified gaschomatographic separation unit and an 8‐fold surface acoustic wave based sensors
(SAW) array detector. For the coffee quality analysis a successful discrimination of three coffee samples could be achieved. The system would be further developed into a fully automated, low cost version that can be broadly used by the coffee producers.

Biological systems enhance the odor discrimination capabilities by performing a small separation of complex mixtures. This principle may be successfully exploited in the development of new sensor platforms. The aim of the presented work is to implement the gas‐chromatographic separation principle for chemical sensing. Herein we report a simple way of imaging gas diffusion through a channel by means of optical changes occurring in a track that contains a chemical indicator embedded in a polymeric matrix.

Odor samples collected in field research are complex mixtures of hundreds if not thousands of compounds. Research is needed to know how best to sample and analyze these compounds. The main objective of this research was to compare recoveries of a standard gas mixture of 11 odorous compounds from the Carboxen/PDMS
SPME fibers, PVF (Tedlar), FEP (Teflon), foil, and PET (Melinex) air sampling bags, sorbent Tenax TA tubes and standard 6 L Stabilizer™ sampling canisters after sample storage for 0.5, 24, and 120 (for sorbent tubes only) hrs at room temperature. The standard gas mixture consisted of 7 volatile fatty acids (VFAs) from acetic to hexanoic, and 4 semi‐VOCs including p‐cresol, indole, 4‐ethylphenol, and 2’‐aminoacetophenone with concentrations ranging from 5.1 ppb for indole to 1, 270 ppb for acetic acid. On average, SPME had the highest mean recovery for all 11 gases of 106.2%, and 98.3% for 0.5 and 24 hrs sample storage time, respectively. This was followed by the Tenax TA sorbent tubes (94.8% and 88.3%) for 24 and 120 hrs, respectively; PET bags (71.7% and 47.2%), FEP bags (75.4% and 39.4%), commercial Tedlar bags (67.6% and 22.7%), in‐house‐made Tedlar bags (47.3% and 37.4%), foil bags (16.4% and 4.3%), and canisters (4.2% and 0.5%), for 0.5 and 24 hrs, respectively. VFAs had higher recoveries than semi‐VOCs for all bags and canisters. New FEP bags and new foil bags had the lowest and the highest amounts of chemical impurities, respectively. New commercial Tedlar bags had measurable concentrations of N, N‐dimethyl acetamide and phenol. Foil bags had measurable concentrations of acetic, propionic, butyric, valeric and hexanoic acids.

Mobile robots equipped with gas sensors can be used for automated measurement tasks including odor trail following, gas source localization, and gas distribution mapping. This article reports on the development of a blimp robot for mapping three‐dimensional gas distribution in indoor environments. The blimp robot is programmed to fly randomly so that its trajectory covers everywhere in the given indoor environment. The blimp is equipped with gas sensors to measure gas concentrations and an ultrasonic
sonar to measure the height from the floor. The measured data are transmitted to an external PC via a wireless communication module. At the same time, a camera placed on the floor takes a picture of the blimp, and its location is recorded with the gas sensor responses. The experimental results indicate that the blimp robot is effective in mapping three‐dimensional gas concentration distribution in indoor environments.

Recent publications in statistical gas distribution modelling have proposed algorithms that model mean and variance of a distribution. This paper argues that estimating the predictive concentration variance entails not only a gradual improvement but is rather a significant step to advance the field. This is, first, since the models much better fit the particular structure of gas distributions, which exhibit strong fluctuations with considerable spatial variations as a result of the intermittent character of gas dispersal. Second, because estimating the predictive variance allows to evaluate the model quality in terms of the data likelihood. This offers a solution to the problem of ground truth evaluation, which has always been a critical issue for gas distribution modelling. It also enables solid comparisons of different modelling approaches, and provides the means to learn meta parameters of the model, to determine when the model should be updated or re‐initialised, or to suggest new measurement locations based on the current model. We also point out directions of related ongoing or potential future research work.

We report on real‐robot odor source localization experiments carried out in an environment with obstacles in the odor plume. The robot was equipped with an ethanol sensor and a wind direction sensor, and the experiments were carried out in a wind tunnel (controlled environment). An enhanced version of the surge‐spiral algorithm was used, which was augmented with a dedicate behavior to manage obstacles (avoid them, or follow their contour). We compare the results in terms of distance overhead and success rate, and discuss the impact of obstacles on plume traversal.

The single odor source declaration in indoor environments by using multi‐robot system is addressed. A three‐step odor source declaration method is put forward, which include robots convergence, odor concentration persistence judgment and odor mass throughput calculation. Initial experimental results in both artificial and natural indoor airflow environments by using three small mobile robots validate the feasibility of the proposed single odor source declaration method.

We report the basic functions and the sensitivity improvement of a chemical sensor system employing a poly‐butadiene (PBD) coated micro cantilever sensor and a carbon‐fiber‐filled adsorption tube. The improvements of the sensitivity were carried out by two methods as 1) reduction of the volume in sensor camber by 1/30, 2) enlargement of the resonance frequency of the cantilever by 4.6 using a high speed analog‐oscillation circuits and a low noise package. Using the 4th vibration mode (resonant frequency 715 kHz) of a PBD coated cantilever (length
width
thickness
) and a small sensor chamber with a volume of 3.5 cc, the sensitivity was enhanced to be 2.4 Hz/ppm for toluene in nitrogen carrier gas with 10 minute adsorption time, which was about 100 times larger than our previous sensor system.

This paper deals with the detection of nitroaromatic explosives. A specific fluorescent material is devoted to the detection of ultra traces of explosives remaining on clothes. The sensor exhibits a large sensitivity for TNT or DNT vapors.

We have developed a new portable electronic nose based on a SAW
sensor array and its readout electronics. The SAW array is based on
non‐continuously working oscillators for sensors coated with different polymer/mesoporous carbon
composite materials. Signals of the SAW array can be obtained by a readout PCB and a microprocessor. Experiments indicate good results for this portable system to perform gas detection and recogntion applications.